1. Field of the Invention
The present invention relates to a hybrid system for and a control method for a vehicle having a first set of road wheels and a second set of road wheels.
2. Description of the Background Art
Hybrid systems utilizing a motor/generator with an engine in moving a motor vehicle are proposed. During starting a vehicle from standstill, it is proposed to use two motors so as to move the vehicle in four-wheel drive mode. This control strategy is possible under condition where the state of charge (SOC) of a battery is high enough to provide overbalance supply of electric energy. However, it involves potential problem that smooth movement cannot be expected, due to uncontrollable torque variations, when the engine has to be started to charge the battery.
According an object of the present invention is to provide a hybrid system and a control method for a vehicle wherein the vehicle can be started from standstill smoothly without relying on two motors.
In accordance with an exemplary implementation of the present invention, a hybrid system for a vehicle having a first set of road wheels and a second set of road wheels is provided. The system comprises an engine controller for receiving a torque request for an engine driving torque and combining an idle speed torque and the engine driving torque to generate an engine torque command signal. An engine, drivingly coupled with the first set of road wheels, applies a first driving torque to the first set of road wheels in response to the engine torque command signal. A hybrid controller is in communication with the engine controller. The hybrid controller generates the torque request and a motor torque command signal taking into account a creep torque portion of the first driving torque and a desired driving torque during starting the vehicle from standstill. A motor is drivingly coupled with the second set of road wheels. The motor applies a second driving torque to the second set of road wheels in response to the motor torque command signal.